Led and method for manufacturing the same

ABSTRACT

An LED (light emitting diode) includes a base, a pair of leads fixed on the base, a housing secured on the leads, a chip mounted on one lead and an encapsulant sealing the chip. The housing defines a cavity to receive the chip. The cavity includes an upper chamber and a lower chamber communicating with the upper chamber. The lower chamber is gradually expanded along a top-to-bottom direction of the LED, and the upper chamber is gradually expanded along a bottom-to-top direction of the LED. The encapsulant substantially fills the lower chamber and the upper chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is related to U.S. patent application Ser. No.______, having Attorney Docket No. “US39669”, entitled “LED AND METHODFOR MANUFACTURING THE SAME”, assigned to the same assignee, anddisclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to LEDs (light emitting diodes) andmethods for manufacturing the LEDs, and more particularly, to an LEDhaving a good waterproof capability and a method for manufacturing theLED.

2. Description of Related Art

As a new type of light source, LEDs are widely used in variousapplications. A typical LED includes a base, a pair of metal leads fixedon the base, a housing formed on the leads, a light emitting chip fixedon the leads and electrically connected to the leads via wires, and anencapsulant attached on the housing and sealing the light emitting chip.The housing is often formed by molding a material of PPA(polyphthalamide) on the two metal leads. However, the attachmentbetween the housing and the leads is unreliable due to poor adherentcapability of PPA to metal. Therefore, moisture of the outsideenvironment may enter the LED through an interface between the leads andthe housing, causing malfunction of the light emitting chip.

What is needed, therefore, is an LED and a method for manufacturing theLED which can overcome the limitations described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present disclosure. Moreover,in the drawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 shows an LED in accordance with a first embodiment of the presentdisclosure.

FIG. 2 shows a first process of manufacturing the LED of FIG. 1.

FIG. 3 is a top view of a semi-finished product obtained from the firstprocess of manufacturing the LED of FIG. 2.

FIG. 4 is similar to FIG. 3, but showing a semi-finished product of anLED in accordance with a second embodiment of the present disclosure.

FIG. 5 shows a second process of manufacturing the LED of FIG. 1.

FIG. 6 shows a third process of manufacturing the LED of FIG. 1.

FIG. 7 shows a fourth process of manufacturing the LED of FIG. 1.

FIG. 8 shows an LED in accordance with a third embodiment of the presentdisclosure.

FIG. 9 shows an LED in accordance with a fourth embodiment of thepresent disclosure.

FIG. 10 shows an LED in accordance with a fifth embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, an LED (light emitting diode) 10 in accordance witha first embodiment of the present disclosure is shown. The LED 10includes a base 11, a pair of leads 12 fixed on the base 11, a housing13 secured on the leads 12, a light emitting chip 14 received in thehousing 13 and electrically connected to the pair of leads 12 and anencapsulant 15 filled in the housing 13 and sealing the chip 14.

The base 11 may be made of plastic such as PPA (polyphthalamide). Thebase 11 may have a rectangular shape. The leads 12 are made of metalsuch as copper or aluminum. The leads 12 are fixed on a top face of thebase 11. The two leads 12 are spaced from each other. Each lead 12protrudes horizontally outside of the base 11 for in electricalconnection with an external circuit (not shown), thereby receiving adriving power for the chip 14 from an external power source (not shown).The base 11 may be formed on the two leads 12 via injection-molding,transfer-molding or other suitable methods.

The housing 13 may be formed on the leads 12 by injection-molding,transfer-molding or other suitable methods. The housing 13 may also bemade of PPA. An outer periphery of the housing 13 is larger than that ofthe base 11 so that a distance between an outer periphery of the housing13 and free ends of the leads 12 is smaller than that between an outerperiphery of the base 11 and the free ends of the leads 12. The leads 12also protrude horizontally outside the outer periphery of the housing13. Also referring to FIG. 6, the housing 13 defines a cavity 131extending from a bottom face 135 to a top face 136 thereof to expose topfaces 126 of the leads 12. The cavity 131 includes an upper chamber 1312and a lower chamber 1311 communicating with the upper chamber 1312. Theupper chamber 1312 has a truncated taper shape with an inner diametergradually decreasing along a top-to-bottom direction of the LED 10. Thelower chamber 1311 has an inner diameter gradually increasing along thetop-to-bottom direction of the LED 10. The upper chamber 1312 has avolume and height larger than that of the lower chamber 1311. An innerdiameter of the cavity 131 at the bottom face 135 is larger than that atthe top face 136. An angle α is defined between an upper portion of aninner circumferential face of the housing 13 defining the upper chamber1312 and the top face 136 of the housing 13. An angle β is definedbetween a lower portion of an inner circumferential face of the housing13 defining the lower chamber 1311 and the bottom face 135 of thehousing 13. The angle α and the angle β are both obtuse angles, andlocated outside of the cavity 131. The angle α is less than the angle β.

The chip 14 may be fixed on one of the two leads 12 by silver epoxygluing, eutectic bonding or other methods. The chip 14 may be a GaNchip, an InGaN chip, an AlInGaN chip or other light emittingsemiconductor chips. The chip 14 is electrically connected to the twoleads 12 via two bonding wires 141. The encapsulant 15 is filled in thecavity 131 to seal the chip 14 and the wires 141. The encapsulant 15 maybe made of epoxy, silicon or other transparent materials. Theencapsulant 15 includes an upper portion 152 filling the upper chamber1312 and a lower portion 151 filling the lower chamber 1311. The upperportion 152 has an outer diameter gradually decreasing along thetop-to-bottom direction of the LED 10, and the lower portion 151 has anouter diameter gradually increasing along the top-to-bottom direction ofthe LED 10. The upper portion 152 has a top face 1520 flush with the topface 136 of the housing 13, and the bottom portion 151 has a bottom face1510 flush with the bottom face 135 of the housing 13. An area of thebottom face 1510 of the encapsulant 15 is larger than that of thehousing 13. Fluorescent material such as YAG (yttrium aluminum garnet),TAB (terbium aluminum garnet), phosphide or sulfide can be uniformlydistributed in the encapsulant 15 to covert the color of light from thechip 14 to a desired color.

The encapsulant 15 made of epoxy or silicon has a larger bonding forcewith the metal leads 12 than that of the housing 13 made of PPA with themetal leads 12. Therefore, as increasing of contact areas between theencapsulant 15 and the leads 12, and corresponding decreasing of contactareas between the housing 13 and the leads 12, the encapsulant 15 can beadhered to the leads 12 more tightly and reliably. The encapsulant 15thus prevents outside moisture from entering the LED 10 and damaging thechip 14.

A method for manufacturing the LED 10 is also disclosed. The methodmainly includes a series of steps as follows.

First, a pair of leads 12 is provided as shown in FIGS. 2-3. The twoleads 12 have two blocking protuberance 18 formed on top faces 126thereof, respectively. The two blocking protuberances 18 may be made ofphotoresist. The photoresist can be designed to have required shape viaphotolithograph technology. In this embodiment, each blockingprotuberance 18 has a strip-like shape with a triangle cross section.Each blocking protuberance 18 extends from a side to an opposite lateralside of a corresponding lead 12 (see FIG. 3), crossing an extendingdirection of the corresponding lead 12. The two blocking protuberances18 are located adjacent to and spaced from two opposite outer free endsof the two leads 12, respectively. Alternatively, as shown in FIG. 4,each blocking protuberance 18 may also have a shape of a U-shapedconfiguration with two feet extending to a corresponding one of twofacing inner ends of the leads 12. The U-shaped structure of theblocking protuberance 18 can reinforce the moisture-proof function ofthe LED 10 to make the LED 10 be hermetical not only to two lateralsides thereof but also to front and rear sides thereof.

A base 11 and a housing 13 are then formed on the leads 12 by molding asshown in FIG. 5. The base 11 and the housing 13 may be separately orintegrally formed, depending on the actual requirements. The base 11 isattached on bottom faces 124 of the leads 12, and the housing 13 isattached on the top faces 126 of the leads 12. A gap 113 between theleads 12 may be filled by the base 11 during molding, or kept empty,also depending on the actual requirements. The housing 13 defines acavity 131 in a central area thereof. The top faces 126 of the leads 12are exposed in the cavity 131. The housing 13 covers a part of eachblocking protuberance 18, remaining the other part of each blockingprotuberance 18 exposed within the cavity 131.

The blocking protuberances 18 are removed by dipping the blockingprotuberances 18 into a chemical solution where the blockingprotuberances 18 are dissolved. A lower portion 16 of the cavity 131 isexpanded laterally to form a wider lower chamber 1311 as shown in FIG.6.

As shown in FIG. 7, a chip 14 is fixed on one of the leads 12 andelectrically connected to the leads 12 through a wire bonding of twowires 141.

Finally, an encapsulant 15 is filled into the cavity 131 to seal thechip 14 in the cavity 131 as shown in FIG. 1.

Furthermore, the leads 12 of the two embodiments may be varied to havedifferent structures. For example, as shown in FIG. 8, the leads 22 eachmay include two horizontal sections 220 and a vertical section 222interconnecting the two parallel sections 220. In addition, as shown inFIG. 9, if the two leads 32 are thick enough to provide sufficientstrength, most parts of the base 11 may be omitted and only a block 110is retained in the gap 113 between the two leads 12. The block 110 isused for increasing the strength of the two leads 22. Alternatively, atop face 111 of the block 110 may also defines two grooves 112 in twoopposite sides thereof as shown in FIG. 10. The two grooves 112 aresymmetrical with respect to each other. The encapsulant 15 may fill thegrooves 112 during molding for further preventing the outside moisturefrom entering the LED 10 from interfaces between the block 110 and theleads 12.

It is believed that the present disclosure and its advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the present disclosure or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments.

1. An LED (light emitting diode) comprising: a pair of leads spaced fromeach other; a chip electrically connected to the leads; a housing fixedon the leads, the housing defining a cavity to receive the chip; and anencapsulant filling the cavity to seal the chip; wherein the encapsulantcomprises an upper portion and a lower portion, the lower portion havinga bottom face joining the leads and a top face connected to the upperportion; and wherein the lower portion of the encapsulant is expandedfrom the top face towards the bottom face thereof.
 2. The LED of claim1, wherein the lower portion of the encapsulant is gradually expandedfrom the top face towards the bottom face thereof.
 3. The LED of claim1, wherein the upper portion of the encapsulant is gradually expandedalong a bottom-to-top direction from the top face of the lower portiontoward a top face of the upper portion.
 4. The LED of claim 1, whereinan angle between an inner circumference surface of a lower portion ofthe housing and a bottom face of the housing is larger than an anglebetween an inner circumference surface of an upper portion of thehousing and a top face of the housing.
 5. The LED of claim 4, wherein aninner diameter of the top face of the housing is less than an innerdiameter of the bottom face of the housing.
 6. The LED of claim 1,wherein the lower portion of the encapsulant has a volume less than thatof the upper portion of the encapsulant.
 7. The LED of claim 1, whereinan area of the bottom face of the lower portion of the encapsulant islarger than an area of a bottom face of the housing joining the leads.8. The LED of claim 1, wherein a block is formed between the two leadsto interconnect the two leads.
 9. The LED of claim 8, wherein the blockdefines two grooves in interfaces between the block and the two leads,respectively, the two grooves being located at a top face of the blockand filled with the encapsulant.
 10. The LED of claim 1 furthercomprising a base fixed to the two leads, wherein the base is attachedto bottom faces of the two leads, and the housing is attached to topfaces of the two leads.
 11. The LED of claim 10, wherein the housing hasan outer periphery larger than that of the base.
 12. The LED of claim 1,wherein the housing and the base are made of the same material.
 13. Amethod for manufacturing an LED (light emitting diode), comprising:providing a pair of spaced leads; forming two blocking protuberances onthe two leads, respectively; forming a housing on the two leads, thehousing defining a cavity therein to expose the two leads, and eachblocking protuberance having a part covered by the housing and anotherpart exposed within the cavity; removing the blocking protuberances toexpand a lower portion of the cavity; fixing a chip in the cavity andelectrically connecting the chip with the leads; and filling anencapsulant in the cavity to seal the chip.
 14. The method of claim 13,wherein the lower portion of the cavity is gradually expanded along atop-to-bottom direction of the LED after removing the blockingprotuberances.
 15. The method of claim 13, wherein an upper portion ofthe cavity is gradually expanded along a bottom-to-top direction of theLED.
 16. The method of claim 13, wherein each blocking protuberance ismade of photoresist, and the blocking protuberances are removed by beingdissolved in a chemical solution.
 17. The method of claim 13 furthercomprising a step of forming a base on the two leads, wherein the baseis attached on bottom faces of the leads, and the housing is attached ontop faces of the leads.
 18. The method of claim 17, wherein the base andthe housing are separately formed.
 19. The method of claim 13, whereinthe leads has a block formed therebetween, the block defining a groovein each lateral face thereof contacting a corresponding lead, the groovecommunicating with the lower portion of the cavity and being filled withthe encapsulant.
 20. The method of claim 13, wherein the encapsulant ismade of epoxy or silicon, and the housing is made of polyphthalamide.